With the continuous development of display technology, OLED display device has become the main trend of the next generation display device due to the advantages of light weight, high contrast, high color gamut, low power consumption, and realizability of flexible display.
Among the OLED display devices, active matrix organic light emitting diode (AMOLED) display has a quick response, and can meet the requirements of display devices with various sizes, so it has attracted attention of many enterprises. AMOLED display device typically comprises an array substrate and light emitting devices, wherein the light emitting devices are mainly realized by a fine metal mask, of which the implementation has become increasingly mature, enabling the mass production of AMOLED.
In the process of realizing the AMOLED, the light emitting device is formed by depositing OLED materials on a low temperature polysilicon back plate with a predetermined sequence by the method for evaporation, and performing a composition process with the pattern on the fine metal mask. As shown in FIG. 1, the structure of an AMOLED display device generally comprises: an array substrate 101, an anode 102, a hole injection layer 103, a hole transport layer 104, a luminescent layer 105, an electron transport layer 106, an electron injection layer 107 and a cathode 108.
Taking the above light emitting device being a top emitting type as an example, during the operation, the light emitted by the luminescent layer will be emitted upwards and downwards respectively; the light emitted upwards is transmitted out through the electron transport layer, the electron injection layer and the cathode; the light emitted downwards is transmitted to the anode through the hole transport layer, the hole injection layer, then reflected upwards by the anode; the reflected light is transmitted out through the hole injection layer, the hole transport layer, the luminescent layer, the electron transport layer, the electron injection layer and the cathode. During the whole luminescent process, when the light is transmitted in the above mentioned layers, it is partially absorbed and scattered due to the optical waveguide effect; the light should be transmitted out of the light emitting device through many layers, therefore the loss of the light emitted from the light emitting device is relatively large, and the external quantum efficiency of the light emitting device is low, which leads to a low light emitting efficiency of AMOLED.